2001 500HO rear brake stepped piston

[pjmartin]

My brakes failed on my first ride and I traced it to the rear brake. Complete fluid loss, smoke coming from rear brake. Pads were new, replaced by previous owner. One pad shows more wear than the other which tells me it was dragging. Disassembled the caliper
-one small o-ring between the halves much thinner than the other. Almost no protrusion so probably leaking.
-crud buildup on exposed part of pistons which probably kept one of them from retracting.
-brake lines reversed, my manual says foot brake to end of piston and hand brake to the step. This may not have contributed to the problem, not sure.

Ordered a new seal kit, but my question concerns one of the pistons. They appear to be anodized aluminum. One is in excellent condition but the other shows signs of pitting where it contacts the seal closest to the pad. If you run your finger over it it feels smooth and you can barely feel the pits with your fingernail. The pitting is just through the anodizing. The interior is blackened and it had the most crud buildup so it probably overheated because it couldn't retract. Tried smoothing with steel wool and 1000 grit sand paper but they wont touch the anodizing.
Piston1.jpg

Piston2.jpg
A new piston will cost me $100. Anyone have an opinion as to whether it should be replaced?

[pjmartin]

I managed to smooth out the pits by spinning it in a lathe and using 1000 grit paper. Fingernail doesn't feel any edges so I'm going to try it out with new rings. Will let you know if it leaks in case anyone else needs the info.

[polman500]

It should work if you got it smooth. You can get a piston kit with seals already installed from Hit the Gas for around $40 if it doesn't work.

[pjmartin]

Not sure what you mean Polman. The seals are fitted in the caliper body so how can you get a piston kit with seals already installed? Will check out the site.

[polman500]

Sorry pj... I didn't pay attention to the year model of sportsman you have. I was thinking of the newer style rear caliper like I just rebuilt on my 06 800. It has a single stepped piston with the seals in grooves on the piston itself. I'd say if you got it slick it should work just fine.

[elmerkit]

Just buy a repair kit and reassemble the whole system and your good to go.

[pjmartin]

I think I'll save the $100 and try the old piston. I'll keep an eye on it and replace it if it ever starts leaking. The pads were new before the ride and now one shows more wear than the other so it was sticking. This heated up the rotor and the thin o-ring between the caliper halves probably leaked fluid onto the rotor causing the smoke and my loss of brakes.

[pjmartin]

Just out of curiosity I removed the bleeders from the caliper body and discovered the real reason for my fluid loss. Previous owner had torqued the bleeder screw too much and broke the seat off the end of the brass part so that the bleeder couldn't seal properly. Piece of brass fell out of the caliper after removing the bleeder assembly. Ordered a new bleeder assembly.
Anyone bleeding this style of rear brake should be careful not to torque the bleeder screws too tight.